As Congress and Trump continue to clash over the Mexico border barrier and restrictive immigration policies, a multi-trillion-dollar issue is being overlooked.

According to the US National Immigration Forum, immigrant-owned businesses employ more than 19 million people and generate $4.8 trillion in revenue.

They also play a major role in rejuvenating regions that have seen economic decline.

Yet immigration policy does not sufficiently address the contributions immigrants make to the nation’s entrepreneurial ecosystem, says Stuart Anderson, executive director of the National Foundation for American Policy.

The main problem, Anderson says, is that there is no visa status for immigrant entrepreneurs.

There are visas for family and employment, such as the HB-1, but none for someone who wants to start a business.

What effect will these policies have? Probably more harm than good.

Research bears this out. Immigration generally improves the government’s fiscal situation, according to a University of Pennsylvania economic impact brief.

Many immigrants pay more in taxes over a lifetime than they consume in government services, the brief concludes.

Documented or undocumented, immigrants are net positive contributors to the federal budget.

Countries shutting the door on legal migration are shooting themselves in the foot says William Kerr, an immigration expert at Harvard Business School.

Kerr has researched the economic effects of global migration of workers for more than a decade.He began with a study of the H-1B visa program, which enables US employers to hire highly skilled foreign workers for three years.

His team’s early findings, in 2001, found that the number of inventions by foreign ethnicities, Indians and Chinese in particular, was closely tied to H-1B admission levels.

Kerr’s team came out with an overall conclusion that suggested US innovation increases with letting in more immigrant scientists and engineers.

The study found little impact, positive or negative, on American Anglo-Saxon workers.

Fast forward to present day and Kerr’s research shows that immigrants contribute to the innovation of large companies, accounting for about 25% of US patent filings.

It’s nigh impossible to find research that suggests immigration is bad for developed economies.

There are negatives:

Native-born residents of states with large concentrations of less-educated immigrants may face larger tax burdens, as these immigrants pay less in taxes and are more likely to send children to public schools.

(According to University of Pennsylvania’s economic impact brief)

So where to family enterprises fit in? Familybusinesses generate 64% of GDP and employ 62% of the workforce, according to Family Enterprise USA, an advocacy group.

And family firms account for whopping 82 million jobs.

Chances are a significant number of immigrants had a hand in the hefty $5.9 trillion family firms bring to the US economy.